Determination of progesterone receptor by hydroxylapatite-column assay

The hydroxylapatite-column assay procedure for progesterone receptors is described. The method is rapid and easy to perform. The receptor proteins bound to labeled ligands are adsorbed on the column at low temperature (2 degrees C) and eluted by ethanol. It is particularly advantageous for measuring receptors in samples of large volume and low protein content. The sensitivity of the technique is much higher than other commonly used methods. The method is capable of detecting progesterone receptor in hamster's uterine cytosol containing protein as little as 13.5 micrograms. The affinity of the receptor can be calculated from specific binding data by Scatchard analysis. Under controlled condition, one point assay can also be applied for receptor determination in small sample with relative confidence.